Iran’s atomic officials said that the country will break the limit on uranium enrichment until European countries curb sanctions.
Iran announced Monday it would breach uranium enrichment limits in 10 days in a move that drew an accusation of "nuclear blackmail" from Washington, but it added that European nations still had time to save the nuclear deal by curbing sanctions.
In an announcement, Iran's Atomic Energy Organization spokesman Behrouz Kamalvandi said, "We have quadrupled the rate of enrichment (of uranium) and even increased it more recently so that in 10 days it will bypass the 300 kg limit."
"Iran's reserves are every day increasing at a more rapid rate," he told state TV, adding that "the move will be reversed once other parties fulfill their commitments."
In an indication of Western concern at Iran's initiative, a White House National Security Council spokesman said the plan amounted to "nuclear blackmail" and must be met with increased international pressure.
Britain said if Iran breached limits agreed under the deal then London would look at "all options." Close U.S. ally Israel, Iran's arch foe, urged world powers to step up sanctions against Tehran swiftly should it exceed the enriched uranium limit.
However, European Union foreign policy chief Federica Mogherini said the EU would only react to any breach if the International Atomic Energy Agency formally identified one.
U.S.-Iran tensions are growing following accusations by U.S. President Donald Trump's administration that Tehran last Thursday attacked two oil tankers in the Gulf of Oman, a vital oil shipping route.
Iran's Armed Forces Chief of Staff, Major General Mohammad Baqeri, Monday denied Tehran was behind the attacks and said if the Islamic Republic decided to block the strategic Strait of Hormuz shipping lane it would do so publicly.
The secretary of Iran's Supreme National Security Council, Ali Shamkhani, said Tehran was responsible for security in the Gulf and urged U.S. forces to leave the region, state TV said.
Tehran said in May it would reduce compliance with the nuclear pact it agreed with world powers in 2015, in protest at the United States’ decision to unilaterally pull out of the agreement and reimpose sanctions last year.
The accord requires Iran to curb its uranium enrichment capacity, capping Iran’s stock of low-enriched uranium at 300 kg of uranium hexafluoride enriched to 3.67 percent or its equivalent for 15 years.
A series of more intrusive U.N. inspections under the deal have verified that Iran has been meeting its commitments.
Urging European signatories to hasten efforts to salvage the accord, President Hassan Rouhani said its collapse would not be in the interests of the region or the world.
"It's a crucial moment, and France can still work with other signatories of the deal and play a historic role to save the deal in this very short time," Rouhani was quoted as saying during a meeting with France's new ambassador in Iran.
Kamalvandi, in a news conference at Iran's Arak heavy water nuclear reactor which has been reconfigured under the deal, said Tehran could rebuild the underground facility to make it functional. Heavy water can be employed in reactors to produce plutonium, a fuel used in nuclear warheads.